The aim of the present study was to evaluate the diagnostic value of plasma human cystatin-S (CST4) in patients with digestive system malignant tumors. CST4 and tumor markers, such as α-fetoprotein (AFP), carcinoembryonic antigen (CEA), carbohydrate antigen (CA)199, CA125, CA153 and CA724, were detected in blood samples from 100 patients with a digestive system malignant tumor and 100 patients with benign digestive system diseases. The tumor markers AFP, CEA, CA199, CA125, CA153 and CA724 were detected using an electrochemiluminescence immunoassay, and CST4 levels were detected using a human CST4 ELISA kit. The results demonstrated that the sensitivities of AFP and CA153 (both 5.00%) were significantly lower than that of CST4 (38.00%) in the diagnosis of digestive system malignancy (P<0.001), and CA724 (18.00%) was also less sensitive than CST4 (P<0.05). The sensitivities of CA199 (26.00%), CEA (31.00%) and CA125 (25.00%) were similar to that of CST4 (P>0.05). There was no significant difference in the CEA, CA125, CA724 and CST4 specificities (P>0.05), which were 91.00, 95.00, 94.00 and 83.00%, respectively. The specificities of AFP (99.00%), CA199 (98.00%) and CA153 (100.00%) were significantly higher than that of CST4 (P<0.01). By constructing a receiver operating characteristic curve and comparing the area under the curve as well as sensitivity, the findings of the present study demonstrated that combining CST4 with AFP, CEA, CA199, CA125, CA153 and CA724 can significantly enhance the diagnostic sensitivity for malignancies of the digestive system. However, the introduction of CST4 into the traditional diagnostic groups (CEA + AFP, CA199 + CA125 + CA153 + CA724 and AFP + CEA + CA199 + CA125 + CA153 + CA724) resulted in an increased sensitivity and loss of specificity, thereby not offering significant advantages in terms of comprehensive diagnostic efficiency compared with the traditional diagnostic groups. In conclusion, CST4 detection may be a promising diagnostic tool. Nonetheless, the potential false positive results in tumor diagnosis should be taken into consideration when developing new diagnostic groups involving CST4.

Many digestive system malignant tumors are characterized by high incidence and mortality rate. Increasing evidence has revealed that the tumor microenvironment (TME) is involved in cancer initiation and tumor progression. Tumor-associated macrophages (TAMs) are a predominant constituent of the TME, and participate in the regulation of various biological behaviors and influence the prognosis of digestive system cancer. TAMs can be mainly classified into the antitumor M1 phenotype and protumor M2 phenotype. The latter especially are crucial drivers of tumor invasion, growth, angiogenesis, metastasis, immunosuppression, and resistance to therapy. TAMs are of importance in the occurrence, development, diagnosis, prognosis, and treatment of common digestive system malignant tumors. In this review, we summarize the role of TAMs in common digestive system malignant tumors, including esophageal, gastric, colorectal, pancreatic and liver cancers. How TAMs promote the development of tumors, and how they act as potential therapeutic targets and their clinical applications are also described.

Chronic inflammation, through a variety of mechanisms, plays a key role in the occurrence and development of digestive system malignant tumors (DSMTs). In this study, we feature and provide a comprehensive understanding of DSMT prevention strategies based on preventing or controlling chronic inflammation. The development and evaluation of cancer prevention strategies is a longstanding process. Cancer prevention, especially in the early stage of life, should be emphasized throughout the whole life course. Issues such as the time interval for colon cancer screening, the development of direct-acting antiviral drugs for liver cancer, and the Helicobacter pylori vaccine all need to be explored in long-term, large-scale experiments in the future.